Missouri’s constitutional ban on gay marriage is being challenged in court by two same-sex couples who say they were denied marriage licenses in Kansas City.

The lawsuit filed by attorneys for the American Civil Liberties Union contends that Missouri’s constitutional provision limiting marriage to one man and one woman violates the equal protection and due process clauses of the U.S. Constitution.

Similar lawsuits have been filed across the country with increasing success in lower courts. Earlier this week, a U.S. appeals court panel in Denver ruled that states cannot prevent gay couples from marrying - a decision that could take the issue one step closer to being decided by the U.S. Supreme Court.

Court records show that the Missouri ACLU lawsuit was filed Tuesday in Jackson County Circuit Court.

ACLU attorney Tony Rothert said Friday that the case wasn’t publicized because supporters didn’t want to district from efforts in St. Louis, where city officials granted marriage licenses to four same-sex couples Wednesday. St. Louis Mayor Francis Slay said the marriage licenses were issued with the intent of challenging Missouri’s ban.

Rothert said the Jackson County lawsuit takes a different strategy by focusing on the denial - instead of the issuance - of marriage licenses but has the same ultimate goal of undoing Missouri’s gay-marriage ban.

"We think it’s unconstitutional, and it’s time to be challenged in a Missouri court," he said.

Missouri Attorney General Chris Koster said after the St. Louis action that he personally supports gay marriage, but he said he is compelled to defend the state constitution. Koster has asked a St. Louis judge for an injunction prohibiting the issuance of marriage licenses to same-sex couples.

House Speaker Tim Jones on Friday criticized the actions of St. Louis officials as "irresponsible." He said supporters of gay marriage should try to get a proposed constitutional amendment placed on the Missouri ballot if they want to repeal the current prohibition.

Instead, "they are trying to push for a change in law to be mandated by the courts, regardless of what the people of Missouri think," Jones, R-Eureka, said in a written statement.

The Jackson County lawsuit was filed on behalf of Kyle Lawson and Evan Dahlgren and Angela Curtis and Shannon McGinty. The lawsuit lists a dozen legal and societal benefits that are denied to same-sex couples because they cannot marry. It says the prohibition furthers no legitimate government interest and "serves only to disparage and injure same-sex couples."

The ACLU is also handling a separate lawsuit filed in February in Jackson County on behalf of several same-sex couples who got married outside of Missouri. It seeks to have those marriages recognized in Missouri.